Designing light-harvesting organic semiconductor microcrystals with wavelength-tunable lasers

phys.org | 5/20/2019 | Staff
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Organic solid-state lasers are essential for photonic applications, but current-driven lasers are a great challenge to develop in applied physics and materials science. While it is possible to create charge transfer complexes (i.e. electron-donor-acceptor complexes among two/more molecules or across a large molecule) with p-/n- type organic semiconductors in electrically pumped lasers, the existing difficulties arise from nonradiative loss due to the delocalized states of charge transfer (CT). In a recent report, Kang Wang and a team of researchers in the departments of chemistry, molecular nanostructure and nanotechnology in China demonstrated the enduring action of CT complexes by exciton funneling in p-type organic microcrystals with n-type doping.

They surrounded locally formed CT complexes containing narrow bandgaps with hosts of high levels of energy to behave as artificial light-harvesting systems. They captured the resulting excitation light energy using hosts to deliver to the CT complexes for their function as exciton funnels in order to benefit lasing actions. Wang et al. expect the preliminary results to offer in depth understanding of exciton funneling in light-harvesting systems to develop high-performance organic lasing devices. The new results are now available on Science Advances.

Semiconductor - Lasers - Spectrum - Interest - Applications

Organic semiconductor lasers that function across the full visible spectrum are of increasing interest due to their practical applications from multiband communication to full-color laser displays. Although they are challenging to attain, electrically pumped organic lasers can advance the existing laser technology to rival organic light-emitting diodes.

Wang et al. formed localized CT complexes by adding a small amount of electron acceptor/donor into the electron donor/acceptor host matrix. The setup contained CT complexes with a narrow bandgap, surrounded by the host matrix with high energy levels to serve as artificial light harvesting antennas. The harvested excitation light energy produced excitons, which were transferred downstream to the acceptors to function as an 'excitation funnel." In...
(Excerpt) Read more at: phys.org
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